In a liquid crystal display device, a TFT substrate in which a pixel electrode and a thin film transistor (TFT) are formed in matrices and an opposed substrate where a color filter is formed at a place corresponding to the pixel electrode of the TFT substrate is installed to be opposed to the TFT substrate, and liquid crystals are interposed between the TFT substrate and the opposed substrate. An image is formed by controlling light transmittance by liquid crystal molecules for each pixel.
Since the liquid crystal display device has a flat shape and a light weight, the use of the liquid crystal display device has been widened to various fields such as a large-sized display device such as a TV, a cellular phone, or a digital still camera (DSC). Meanwhile, a viewing angle characteristic is problematic in a liquid crystal display device. The viewing angle characteristic is a phenomenon in which luminance is changed or chromaticity is changed when a screen is viewed from the front side and when the screen is viewed from an inclined direction. An in plane switching (IPS) mode in which the liquid crystal molecules are operated by horizontal electric fields has an excellent viewing angle characteristic.
As a method of performing alignment processing of an alignment film used in the liquid crystal display device, that is, granting an alignment control capability, a method of processing by rubbing as the related art is used. In the alignment processing by the rubbing, the alignment processing is performed by rubbing the alignment film with a cloth, but meanwhile, there is an optical alignment method of granting the alignment control capability by non-contact with the alignment film. Since the IPS mode does not need a pretilt angle, the optical alignment method can be applied. Japanese Patent Application Laid-Open Nos. 2004-86047, 2004-20658, 2004-163646, 2004-341030, 2004-346311, 2005-215029, and 2006-17880 are known examples associated with the optical alignment film and they disclose that a cross-linking reaction, a cleavage reaction, or a dimerization reaction of the molecules is caused within a thin film by irradiating linearly polarized ultraviolet rays and anisotropy is granted to an arrangement of the molecules within the thin film.